1. Field of the Invention
The present invention relates to a method and apparatus for wrapping products such as napkins, rolls of toilet paper and paper towels. More particularly, the present invention relates to a method and apparatus for the continuous wrapping of products, wherein a continuously fed wrapping material is formed into a tube, articles are fed into the tube, and the tube is separated between the sequential units of products at spaced intervals by a heated cutting element moving along the path of the tube.
2. Discussion of the Related Art
A wide variety of consumer products are mass production wrapped in a heat sealable wrapping material before being delivered to the customer. For example, numerous paper products such as napkins, paper toweling rolls, or toilet paper rolls are wrapped in a thermoplastic material such as polyethylene. The thermoplastic wrapper serves to hold the articles tightly together and to protect them from moisture and abrasion.
As is often the case for products prepared for the consumer mass market, the cost per unit article is strongly dependent on the amount of time required for each operation, including packaging. Known prior art wrapping machines require the product to be displaced from its direction of motion several times during the packaging operation to produce a sealed overwrap of heat sealable material around the product and then to fold and heat seal the ends of the packaging about the product. The displacements and reciprocations of the product within the machine limits the production speed because of the time that must be allocated to such motions. Additionally, the motions of the machine parts required to change the direction of motion of the articles invariably leads to shock and vibration which can become severe as machine speed is increased. In addition, the mechanism for separating the heat sealable material is also crucial to the performance and efficiency of the machine. In many prior art devices, the speed of the wrapping machine is often limited by reason of having to cut a tube transversely as it is continuously fed forward. The cutting step makes it difficult or impossible to achieve a fully compressed or tightly wrapped product.
The below-referenced U.S. patents disclose embodiments that were at least, in part, satisfactory for the purposes for which they were intended. The disclosures of all the below-referenced prior United States patents in their entireties are hereby expressly incorporated by reference into the present application for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.
U.S. Pat. Nos. 2,545,243; 2,982,334; 3,011,934; 3,050,916; 3,133,390; 3,153,607; 3,325,331; 3,576,694; 4,054,474; and 4,084,999 disclose various methods for the formation of a heat sealed wrapper about an article. Many of these references, while somewhat satisfactory for their intended purpose, operate on reciprocating motion and include numerous moving parts in, e.g., their flighted infeed systems. The flighted infeed systems disclosed are often slave driven by the upstream folder machines and as a result, flight jams are commonly caused by timing issues.
U.S. Pat. No. 4,430,844 to James discloses a machine capable of forming sealed wrappers around articles. The machine disclosed in the James patent achieves separation of articles by introducing transverse lines of weaknesses into a flat film at measured intervals representing the wrapper length. The film is then formed into a tube and articles to be wrapped are introduced into the continuously moving tube. Separation into individual packages is achieved as leading wrapped package is pulled forward at a higher speed thereby severing it from a tube at the line of weakness. Although this method works for film or paper wrapping material, special care must be taken to ensure good film tension control as well as perforation geometry in order to avoid premature separation. The machine is also extremely sensitive to variations in film properties and does not allow for product compression.
U.S. Pat. No. 4,218,863 to Howard et al. also discloses a method and apparatus for forming sealed wrappers around articles. The machine disclosed in the Howard patent achieves separation of articles by cutting of the tubular film with a rotating serrated knife. The disclosed method works for film, but it is generally limited to single roll products.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved system, apparatus and method for wrapping articles. It is preferred to have a wrapping machine that can receive articles to be wrapped and form an overwrap on the articles in substantially continuous motion through the machine. It is further desirable for a continuous motion wrapping assembly that allows much higher production speeds to be obtained. There is a further need for improvements to the infeed systems and cutting systems of known continuous motion wrapping assemblies. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.